What are the concrete markers scattered around Decatur GA that have marking on them?|176715

Walking down the street anywhere near emory you pass these 18 inch or so tall and 4 inch wide in both directions concrete rectangular blocks. They have engravings on them that vary. The one i most recently passed had _R/W_ written down the side, and most if not all have an x on top.

They are called Right-of-Way Markers